1. Field
The field of the invention is devices for positioning towing vehicles for engagement of hitches with trailers and the like. More particularly, the invention is concerned with indicators visible to the operator of the towing vehicle, showing the relative position of the mating elements of the connecting hitches.
2. State of the Art
Typically, hitches for connecting towing vehicles with trailers include a coupling ball upon the vehicle and a mating socket upon a forwardly projecting tongue upon the trailer Both ball and socket are located centrally, at bumper level, and are thus not in direct view by the vehicle operator. Hookup requires much trial and error, the unaided operator typically dismounting repeatedly to check the ball position relative to the socket. Damage to the vehicle or trailer is a real possibility with such blind maneuvering. Many sighting devices have been put forth to solve this problem. Most such devices include a pair of co-operating visual aids, one secured to the trailer and the other secured to the towing vehicle, so that alignment of the hitch components may be made by maneuvering the vehicle from the driver's seat. Representative of these are U.S. Pat. Nos. 3,918,746, 4,285,138 and 4,065,147. Most of these devices are either impractical, easily damaged, or prohibitively expensive. Some hitching assemblies have complicated pivoting components and mechanical guiding members permitting less precise positioning of the vehicle by the operator. (U.S. Pat. Nos. 2,197,157 and 2,844,390)
Other devices recognize the shortcomings of all of the line of sight devices, and provide for "blind" coupling, depending upon electronic sensors, signal transmitters and the like.
Many of these devices, however, are electromechanical, in that some physical connection between the towed and the towing vehicle is necessary. U.S. Pat. No. 4,030,775 utilizes a spool of wire with a micro-switch connected to a display to show how much of the wire is extended or retracted, which indicates relative coupling positions of the hitch components. Similarly, U.S. Pat. No. 4,432,563 utilizes a wire, with the added provision for indication of the direction of deviation of the wire from axial alignment as the towing vehicle maneuvers. Other patents utilizing a combination of electronics, display, and switching devices include U.S. Pat. Nos. 2,797,406 (hitch contact switches carried by towing vehicle), 3,418,628 (position switches tripped by ball) and 4,187,494 (flexure of a member utilized as a sensing means for indication of relative angular and linear positions). U.S. Pat. No. 3,825,921 utilizes a wave emitter on the towing vehicle and a wave receiver coil on the trailer. A current is induced in the coil, which is monitored to show relative positions of the emitter and receiver coils. The physical connection between the towing and the towed vehicles is in this case an electrical conductor. However, a considerable number of components and electrical controls are necessary. In contrast, U.S. Pat. No. 3,924,257 employs no mechanical connection between the trailer and towing vehicle. However, an electrically powered transmitter must be provided on the trailer and a separately powered receiver on the towing vehicle.
Thus, all prior art devices, whether purely mechanical line of sight, electro mechanical, or completely electrical, are complex and expensive, perhaps more so than justified for solution to the problem. Clearly, there is a need for an effective trailer hitching aid which avoids the complexity and expense of line of sight devices, electromechanical combinations, and needlessly sophisticated electronics.